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3124
Enzymes
Enzymes are proteins that are found in all cells. They speed up
chemical reactions to allow cells to function properly.
Enzymes (3124)
At the end of this unit of study you should be able to do the following:
1. Explain the function of enzymes
2. List and explain the 3 factor that affect how well an enzyme functions.
3. Use the following word correctly:
enzyme
substrate
concentration
temperature
pH
pH scale
acid
neutral
base
amylase
denatured
Enzymes (3124)
All living things need enzymes in order to stay alive. Enzymes are proteins
found in all cells. Enzymes speed up certain chemical reactions, like
photosynthesis. Without enzymes, certain chemical reactions that keep a cell alive
could not happen fast enough.
There are 3 things that influence how well an enzyme works:
1. concentration of the enzyme/substrate
2. pH
3. temperature
REMEMBER THIS !!!
The function of an enzyme is to speed up certain chemical reactions that
support life.
1. Concentration of Enzyme/Substrate
Enzymes must attach to a substrate before they can work properly. A
substrate is the reactant the enzyme binds to in a cell to speed up the
chemical reaction. This process has been compare to a lock and a key. The enzyme
would be the key and the substrate would be the lock. They must both be present
before anything happens. The more substrate is present, the better the
enzyme works. If too little substrate is present, the reaction may proceed too
slowly to be of any use to the cell.
REMEMBER THIS !!!
The concentration of the substrate and enzyme determines how fast the
reaction will occur. If there is too little enzyme or substrate, the reaction
may be too slow to maintain life functions.
Question 1. What is the function of enzymes?
Question 2. What would happen to the rate of chemical reactions in cells if the
number of enzymes and/or substrates were reduced?
Interesting Scientific Fact: One of the enzymes in saliva, amylase, begin the
process of carbohydrate digestion in your mouth.
Above, we compared substrates and enzymes to a lock and key. The reason
a key works on only one lock is due to the specific shape of that key. If
you wore down the teeth on the key, changing its shape, the key would no
longer work. The same thing would happen to an enzyme if you changed its
shape. The next two factors can change the shape of the enzyme, pH and
temperature.
2. pH
pH is the measure of whether something is acidic, neutral, or basic. The pH
scale indicates how acidic or basic a solution is and includes the numbers 1-14. The
smaller the pH number, the more acidic a solution will be. The pH number 1 is
more acidic than the pH number 3, for instance.
The pH number 7 is considered neutral. pH 7 is neither acid or base. It is
neutral.
The higher the pH number, the more basic a solution. A mixture with a pH
of 13 is more basic than a mixture with a pH of 11.
Each enzyme has an optimal pH, a pH in which they like to work the fastest.
The optimal pH can be thought of as the enzyme’s favorite pH. Most living things
operate best at a pH near 7. Remember, water is the major component in a cell.
If the pH of the water solution in a cell becomes too acidic or basic, the enzymes
do not function properly and the cell usually dies unless the pH is corrected.
Changing the pH would be like filing down the teeth of the key.
REMEMBER THIS !!!
Most living things require their cells to be around a pH of 7. If the pH is too
low or too high, the enzymes in the cells do not work and the cell usually dies.
Question 3. In the space below, write an explanation of pH to someone who has
never heard of it?
Question 4. Why is the shape important to an enzyme? What factors can change
the shape of an enzyme?
Question 5. Why is pH important to enzymes?
Interesting scientific Fact: The pH of a human stomach may go as low as a very
acidic pH of 1 when digesting certain foods. Carbonated soft drinks have a pH
around 3.5; milk, on the other hand, has a pH of 6.5; bay water has a pH of 8.5;
while household ammonia has a very basic pH of 12.
2. Temperature
Enzymes also have an optimal temperature in which they function properly.
If the temperature is too high or too low, they do not function. The correct
temperature is important for the enzymes to function properly
Since temperature affects enzymes, for humans it is very important to
maintain the correct internal temperature. Humans live in a very narrow
temperature range. If your body temperature falls more than 10 degrees, you feel
very cold and your enzymes move too slowly to be effective. If you internal body
temperature is more than 10 degrees above normal, you feel very hot and the
protein in the enzymes may become denatured. In either case, extreme
temperatures affect enzyme activity. When an enzyme cools down to much, their
shape changes, kind of like bending the key. When an enzyme heats up, it is
actually denatured, or destroyed. This would be like melting the key.
REMEMBER THIS !!!
Enzymes work best at certain temperatures. They do not work at extreme
temperatures.
Question 6. How would you define temperature?
Question 7. How does temperature affect enzyme activity?
Interesting Scientific Fact: The correct temperature is very important to all
living things, including humans. As you know, enzymes only work at certain
temperatures. It is possible for a living thing to die without the temperature
falling below the freezing line.
Summary
Enzymes are a type of protein that speeds up chemical reactions within all
living things. Enzymes work to help living things stay alive. If the enzymes fail to
work properly, the living thing usually dies.
Enzymes have 3 things that affect how well they work.
The first is temperature. Your body has thousands of enzymes, each very vital
to the chemical reactions of a cell. Temperature is a very critical factor to the
reactions that keep a cell alive, for if the temperature is too cold, then the
chemicals move too slowly, and the chemical reactions don’t occur fast enough to
support life. If the temperature is too high, the enzymes, which are needed to
speed up the reactions, become denatured (destroyed).
The second condition for proper enzyme function is pH. Enzymes also need
to be in a specific pH, or else they may become denatured. The pH scale
determines whether a solution is acidic or basic. A pH of 1 – 6 indicates an acidic
solution. A pH of 7 indicates a neutral solution. A pH of 8-14 indicates a basic
solution. Most enzymes work best in a pH range of 6 – 8.
The third condition is the enzyme/substrate concentration. Remember the
lock and key example. If there are not enough keys for the locks, then some of
the locks do not get opened. It is the same for enzymes. If there is not enough
substrate, then the enzymes do notfunction as well as they should. The
concentration of enzymes and their substrates are important to the proper
functioning of the enzymes.
Question 8. Without looking, list and explain the 3 factors that affect enzyme
activity.
Question 9. Explain how substrates and enzymes behave much like a lock and key.
Enzymes
Test Yourself
Matching
_____ 1. enzymes
a. used to determine if a solution is an acid, neutral or a
base.
_____ 2. temperature
b. the reactant in a reaction that an enzyme attached to
_____ 3. substrate
c. the amount of enzyme/substrate present in a solution
_____ 4. amylase
d. what enzymes are mostly made of
_____ 5. concentration e. a factor that affects the enzymes ability to work
_____ 6. protein
f. the destruction of a protein
_____ 7. denaturing
g. a protein that speeds up chemical reactions
_____ 8. pH scale
h. an enzyme that found in saliva breaks down
carbohydrates
True or False
_____ 1. Enzymes are carbohydrates.
_____ 2. Enzymes are proteins.
_____ 3. Enzymes speed up chemical reactions in a cell.
_____ 4. Each enzyme attached to a specific substrate in a chemical reaction
_____ 5. The pH of a solution affects how well an enzyme works
_____ 6. Amylase is an enzyme that helps break protein into glucose.
_____ 7. Temperature has no effect on enzyme activity
_____ 8. If amylase is denatured, it works better
_____ 9. If amylase is denatured, it can still break down carbohydrates
_____10. If amylase is denatured, it cannot break down carbohydrates
_____ 11. pH determines the amount of enzyme/substrate concentration in a cell
_____ 12. pH and temperature are the only factors that affect the activity of an
enzyme.
_____ 13. Temperature is a measure of how much heat is present
Completing Sentences
enzyme
denatured
chemical reactions
pH
substrate
temperature
amylase
1. ____________________ is an enzyme that breaks down carbohydrates.
2. When a carbohydrate attaches to an __________ molecule, it is digested.
3. Each enzyme needs a __________________ to work correctly
.
4. An ________________ is a protein that speeds up chemical reactions in a cell.
5. If an amylase molecule becomes __________________, it will not work
correctly.
6. There are thousands of different enzymes that control the
_______________________
within a cell.
7. _____________ determines whether a solution is an acid, neutral, or base
8. An enzyme will work best within a narrow pH and ____________________
range.
9. If the temperature becomes too high, an enzymes may become useless because
it has become ___________________________.
10. If the _________ is too low, the solution is acidic.
True or False
_____ 1. Temperature is very important to the cell.
_____ 2. High temperatures cause the reactions in a cell to slow down too much.
_____ 3. Most enzymes work best in a pH of 1 to 3.
_____ 4. A neutral solution has a pH of 14.
_____ 5. Cool temperatures make the chemical reactions slow down too much.
_____ 6. The pH scale measures the strength of an acid or a base.
_____ 7. An acid is indicated by a pH level between 8 and 14.
_____ 8. An acid is indicated by a pH level between 1 and 6
Completing Sentences – Words may be used more than once.
pH scale
denatured
high temperatures
acid
low temperatures
base
neutral
1. Enzymes are described as __________________ if they are destroyed.
2. Enzymes may be denatured if they are exposed to __________________ or
__________________.
3. The ________________ is used to measure whether a solution is acidic or
basic. solution
4. A solution that has a pH between 1 and 6 is an ________.
5. A solution that has a pH of 7 is ______________.
6. A solution that has a pH between 8 and 14 is a ___________.
7. _______________________ cause the molecules to move too slowly to allow
chemical reactions to happen fast enough.
8. Enzymes usually work best around a _____________________ pH.
Answer the following.
1. What does it mean to say a protein is denatured?
2. How would you describe an enzyme?
3. List and explain the 3 factors that affect how well an enzyme is able to
function.
4. What is a substrate? Why are they important to enzymes?
5. What happens to a reaction if an enzyme is in a very cold solution?
6. What happens to a reaction if an enzyme is in a boiling solution?
7. What happens to a reaction if an enzyme is in a very low pH?
8. Predict what would happen if all of the enzymes in a living organism would stop
functioning.
Enzymes
Answer Sheet
Question 1. What is the function of enzymes?
Question 2. What would happen to the rate of chemical reactions in cells if the
number of enzymes and/or substrates were reduced?
Question 3. In the space below, write an explanation of pH to someone who has
never heard of it?
Question 4. Why is the shape important to an enzyme? What factors can change
the shape of an enzyme?
Question 5. Why is pH important to enzymes?
Question 6. How would you define temperature?
Question 7. How does temperature affect enzyme activity?
Question 8. Without looking, list and explain the 3 factors that affect enzyme
activity.
Question 9. Explain how substrates and enzymes behave much like a lock and key.